Air operated sanding machine



Sept. 3, 1968 O. HENDRICKSON 3,399,494

AIR OPERATED SANDING MACHINE Filed June 14, 1965 4 ShGGtS -ShQGT. 1

1 Of/o Hendr/t/rson 1N VENTOR.

P 3, 1968 o. HENDRICKSON 3,399,494

AIR OPERATED SANDING MACHINE Filed June 14, 1965 4 Sheets-Sheet 2 Fig.5

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m I Otto Hendr/fckson 2/2 L 208 INVENTOR.

P 1968 o. HENDRICKSON 3,399,494

AIR OPERATED SANDING MACHINE Filed June 14, 1965 4 Sheets-Sheet 5 V 1 IOffo Henar/c/rson INVENTOR.

Sept. 3, 1968 o. HENDRICKSON 3,399,494

AIR OPERATED SANDING MACHINE Filed June 14, 1965 4 Sheets-Sheet 4 OttoHendr/ckson 1N V15 N TO K United States Patent 3,399,494 AIR OPERATEDSANDING MACHINE Otto Hendrickson, Riverside, Calif., assignor 0fone-third to Al Lohbeck, Arcadia, Calif. Filed June 14, 1965, Ser. No.463,511 9 Claims. (Cl. 51-62) ABSTRACT OF THE DISCLOSURE A pneumaticallydriven rubbing machine including a piston reciprocated by means of analternately directed flow of compressed air which is eifectuated byinserting a flow directing valve in series with an air intake. Expansionof air against one end of the piston causes a stroke in one direction.The valve is coupled to the piston so that motion of the piston causesrotation of the valve which in turn re-directs the air intake to theopposite end of the piston resulting in an oppositely directed stroke.The piston is gear-linked to a reciprocating rubbing member whichoperates upon a work surface.

The present invention generally relates to an air operated sandingmachine and more particularly to such a machine having certain novelstructural features therein which enable a more effective operation of asanding or operating element driven by a pneumatic motor.

One object of the present invention is to provide an air operated sanderincluding an air motor having a reciprocating piston therein in whichthe piston rings on the piston are expanded by air pressure so that theair pressure when driving the piston will at the same time expand therings against the cylinder wall so that the piston rings will besealingly retained against the cylinder wall carrying both the powerstroke and exhaust stroke of the piston.

Another object of the present invention is to provide an air operatedsanding machine having an air motor for driving an abrading elementincorporating a novel valve assembly therein, which employs portsorientated directly across from one another so that at the same instantair begins to enter one cylinder, it is exhausted from the othercylinder. Incorporated into the assembly is a slightly slack or lag atthe actuator and valve joint thus permitting the valve to stay open fora period of time when the piston is moving on the power stroke beforebeginning to close the inlet port thus keeping the exhaust open on theother side of the piston and in the other cylinder for better venting ofthe other cylinder.

Yet another object of the present invetion is to provide an air operatedsanding machine having a motor of the reciprocating piston typeconnected with a sanding shoe or the like in which the piston travels inthe opposite direction to the sanding shoe with there being equal forceexerted against the cylinder head connected to the machine body and thepiston which forces the machine body toward the direction the sandingshoe is moving. Thus, the harder one presses on the machine, the morethe air driving the machine will help to balance the machine.

A further important feature of the present invention is to provide anair motor for driving a sanding machine including a reciprocating pistonand oscillating valve assembly orientated with the piston close to thecenter of the machine body thereby substantially eliminating side wiggleof the machine thus reducing fatigue incident to operation of themachine. Further, the structure of the interconnection between thepiston and the sanding shoe permits the piston to be placed very closeto the bottom of the machine thus overcoming up and down motion of themachine body.

A still further significant feature of the invention is to provide amachine body with a cylinder extending therethrough with each end of thecylinder forming a working cylinder and each end of the cylinder beingclosed by a cap at the end thereof to prevent air blow-by due to thecylinder being close to the bottom of the machine body.

Another feature of the present invention resides in its relativesimplicity of construction, compactness, dependability, ease of assemblyand repair and relatively inexpensive manufacturing cost.

These together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout, and in which:

FIGURE 1 is a top plan view of the air operated sanding machine of thepresent invention;

FIGURE 2 is a side elevational view of the air operated sanding machineof this invention;

FIGURE 3 is a transverse, sectional view taken substantially upon aplane passing along section line 3-3 of FIGURE 2 illustrating theorientation of the valve and the operating handle therefor;

FIGURE 4 is an end view of the present invention as viewed from theright hand end of FIGURE 2;

FIGURE 5 is a longitudinal, plan sectional view taken substantially upona plane passing along section line 5-5 of FIGURE 2 with certain areas ofthe structure being broken away;

FIGURE 6 is a longitudinal sectional view taken substantially alongsection line 6-6 of FIGURE 5 illustrating further structural details ofthe invention illustrating in particular the construction of theoscillating valve;

FIGURE 7 is a transverse, sectional view taken substantially upon a planpassing along section line 7-7 of FIGURE 5 illustrating furtherstructural details of the machine body and oscillating valve;

FIGURE 8 is a perspective view of the reciprocating piston employed inthe air motor;

FIGURE 9 is a longitudinal sectional view taken substantially upon aplane passing along section line 9-9 of FIGURE 6 illustrating themechanism for reciprocating the sanding shoe;

FIGURE 10 is a perspective view of the valve body and the oscillatingvalve member;

FIGURE 11 is an exploded perspective view of the valve body and valvemember illustrated in FIGURE 10 with the bearings omitted;

FIGURE 12 is a detail sectional view taken substantially along a planepassing along section line 12-12 of FIGURE 6 illustrating the structureof the valve member and its association with the valve body;

FIGURE 13 is an end view of the right hand end of the machine with theend plate exploded therefrom;

'FIGURE 14 is an end view similar to FIGURE 13 but illustrating the leftend View of the machine;

FIGURE 15 is a detailed sectional view taken substantially upon a planepassing along section line 15-15 of FIGURE 6 illustrating the air flowpassage and pressure seal arrangement for the cylinder and the expansionpassage for the piston rings; and

FIGURE 16 is a detailed sectional view taken substantially upon a planepassing along section line 16-16 of FIGURE 15 illustrating furtherstructural details of the cylinder seal and piston rings and the airpassageways.

Referring now specifically to the drawings, the air operated sandingmachine of the present invention is generally designated by the numeral10 and includes an air motor 12 and a sanding pad 14 which is driven ina reciprocating manner by the air motor 12. The air motor 12 includes aone-piece block or body 16 of generally rectangular configuration buthaving longitudinally extending concave areas 18 in the side wallsthereof to provide rounded and outwardly flared upper corners 20 toprovide means for effectively gripping the machine with the thumborientated in one concave area and the ends of the fingers orientated inthe other. All of the fingers could be provided in one concave area orthe forefinger could be orientated along the top surface of a downwardlycurved forward end 22 of the body 16. The size, shape and dimensions ofthe body as just defined enables a person to conveniently support andmove the sanding machine by grasping the body 16 in the mannerdescribed.

The body 16 has a longitudinal passageway extending therethrough in theform of a bore 22 which is of constant diameter with the end portionsthereof defining cylinders 24 and 26. The bore 22 receives areciprocating piston generally designated by numeral 28 which includesoppositely disposed piston heads 30 and 32 interconnected by a narrowcentral portion 34 that is partially cylindrical and the piston heads 30and 32 are cylindrical in configuration and each piston head 30 and 32includes a peripheral groove 36 disposed adjacent the respective pistonhead such as the head 32 illustrated in FIGURE 16. A pair of splitpiston rings 38 are disposed in each groove 36 with the slit in therings being inclined as at 40. The piston rings 38 are constructed of aplastic-type material which has considerable wear resistance and isrelatively easy to lubricate or provided with impregnated lubrication.Communicated with the groove 36 is a pair of diametrical passageways 42and 44 with the passageway 42 communicating with the portion of thegrooves 36 underlying one of the rings 38 and the passageway 44communicating with the groove 36 underlying the other of the rings 38.The passageways 42 and 44 are communicated with each other by alongitudinal passageway 46 which intersects both the passageways 42 and44 and extends to the surface of the piston head such as the piston head30 illustrated in FIGURE 16. Thus, the air exerting pressure on thepiston head 30 will also pass inwardly through the passageway 46 andthen radially outwardly through the passageways 42 and 44 for urging thesealing rings 38 outwardly in relation to the groove 36 into sealingcontact with the wall of the cylinder 26 for sealing the piston 28 inrelation thereto during reciprocation thereof.

The ends of the piston heads 30 and 32 have a chamfered peripheral edge48 to facilitate their reciprocation and the narrow central portion 34of the piston 28 is provided with end shoulders 50. Disposed between theshoulders 50 adjacent the lower end edge thereof is a mounting plate orgear plate 52 having a plurality of gear teeth 54 extending from onesurface thereof thus forming a rack gear rigid with the piston 28. Therack gear is generally designated by numeral 56 and the plate 52 thereofis secured to the central portion 34 of the piston 28 by rivet typefasteners 58 which have the heads thereof received in recesses 60 formedin the opposite wall of the central portion 34. Also received in eachrecess 60 is a wick 62 in the form of a cylindrical absorbent pad whichare in the form of oil wicks and which will conform to the internalsurface of the bore 22 for facilitating lubrication of the wall of thebore 22 during reciprocation of the piston 28.

Disposed vertically in the body 16 is a bore 64 receiving a generallycylindrical valve body 66 that is secured in the bore 64 by a press fitor in a removable manner if desired. Disposed in said valve body 66 isan oscillating valve member generally designated by numeral 68 and avalve actuator generally designated by the numeral 70 which includes atubular member 72 having a spur gear 74 on the lower end thereof withthe spur gear 74 and tubular shaft 72 being of one-piece construction.The spur gear 74 has peripherally spaced gear teeth 76 thereon which arein meshing engagement with the gear teeth 54 on the rack gear 56. Thus,when the rack gear 56 is reciprocated due to reciprocation of the piston28, the valve actuator 70 will also be oscillated about the longitudinalaxis of the tubular shaft 72. The upper end of the tubular shaft 72 isprovided with a semicylindrical recess 78 which extends diametrically ofthe tubular shaft and thus defines a pair of longitudinally extendingshoulders or lobes 80 which are disposed at diametrically opposed pointson the tubular shaft 72. A cylindrical insert 82 is press fitted intothe valve body or sleeve 66 and includes a central bore 84 whichreceives the upper end portion of the tubular shaft 72 with the bottomof the recess 78 generally aligned with the bottom of the insert 84. Theinsert 84 is provided with a pair of diametrically disposed arcuateslots 86 and 88 therein for a purpose described hereinafter.

The valve member 68 is in the form of a cylindrical rod-like body 90having an upper axial extension 92 of slightly less diameter with thejuncture between the cylindrical body 90 and the projection 92 beingformed by a peripheral shoulder 94 which supportingly engages the upperend of the insert 82 with the cylindrical body 90 being rotatablydisposed in the bore 80 and the projection 92 being disposed above theinsert 82 as illustrated in FIGURE 6.

The lower end of the valve member 68 is provided with a recess 96 whichdefines a pair of axial shoulders or lobes 98 engageable with theshoulders or lobes on the tubular shaft 70 whereby the actuator 70 willbe drivingly joined or connected with the valve member 68 foroscillation thereof in response to oscillation of the tubular shaft 72.While the shoulders or lobes 80 are disposed diametrically across thetubular shaft 72, the shoulders or lobes 98 are angularly disposed withthe extent of the cylindrical portion between the lobes 98 being lessthan one-half a circle thus providing a space or slack 100 between oneof the lobes 98 and one of the lobes 80 when the valve actuator andvalve are assembled.

The two lobes 98 on the cylindrical body 90 are formed by a longitudinalgroove or slot 102 communicating with the bottom edge of the valvemember at a point between the shoulders 98 and extending upwardly anddiametrically of the cylindrical body 90 to a point generally midway thedistance between the shoulder 94 and the recess 96 as illustrated inFIGURES 6 and 11. The groove or slot 102 has a smoothly arcuating bottomfor guiding air therethrough in a manner described hereinafter.

The upper end of the valve member 68 is also provided with a slot orgroove 104 which has an arcuate bottom surface which terminates inspaced relation to the bottom end of the cylindrical body 90 andgenerally slightly above the horizontal plane of the recess 96. Theupper end of the slot or groove 104 extends to the top surface of theprojection 92 as illustrated in FIGURES 6 and 11 for inlet of air in amanner described hereinafter. A screw-threaded cap 106 is threaded intothe internally threaded upper end portion 108 of the valve body orsleeve 66 with a suitable O-ring or other seal 110 being provided forthe cap 106 and with the cap 106 including a polygonal socket 112 forreceiving a suitable wrench. By removing the cap 106. the valve member68 may be removed by turning the machine upside down so that the valvemember will drop out thus enabling another valve member to be insertedwith the valve members having different slack or lag characteristics fordetermining the length of stroke of the sanding shoe 14. If a longerstroke is desired more clearance between the lobes 80 and 98 should beprovided.

For rotatably supporting the tubular shaft 72, there is provided a pairof ball bearing assemblies 114 and 116 which are press fitted onto theexterior surface of the tubular shaft 72 and into the interior surfaceof the sleeve or body 66. Inner and outer spaces 118 and 120 areprovided with the spacer 118 spacing the inner races of the ball bearingassemblies 116 and 114 and the outer spacer 120 spacing the outer racesof the ball bearing assemblies 114 and 116.

Also, the sleeve or body 66 is provided with a pair of diametricallyopposed circumferential slots 122 and 124 therein which are aligned withthe slots 86 and 88 respectively. Disposed above the slot 122 is anarcuate slot 126 which is an inlet slot. The slot 126 is a high pressureinlet slot and is slightly offset in relation to the rear port 122. Asillustrated, the upper end of the insert 82 is aligned with the loweredge of the port 126 and the shoulder 94 and groove 104 is communicatedwith the chamber defined by the interior of the valve sleeve or body 66,the closure cap 106 and the reduced projection 92 so that high pressureair enters the inlet port 126 and is at all times communicated with theslot or groove 104.

For supplying high pressure air to the high pressure inlet port 126, thebody 16 is provided with an inlet passageway 128 that extends rearwardlyfrom the port 126 to a rear head 130 which includes a passageway 132communicating with the passageway 128 and which is retained in place bysuitable fastening screws 134 or the like. The passageway 132 is ofangular orientation and extends into a valve body 136 that is integralwith the head 130. The valve body includes an inlet passageway 136having a suitable fitting 138 attached thereto by which a high pressureair inlet hose 140 is connected to the passageway 136. The passageway136 is connected to the passageway 132 through a valve seat 142 that isengaged by a ball valve member 144 having a stem 146 extending upwardlytherefrom through a suitable guide 148. A spring 150 retains the ballvalve 144 against the seat 142 and the spring 150 is retained in placeby a retaining plug 152. The upper end of the valve stem 146 is roundedand engages the surface of an elongated operating handle 154 that hasdepending lugs or ears 156 pivotally attached to the valve body 134 bypivot bolt or pins 158. The operating end 160 of the handle extendslongitudinally of the top surface of the body 16 in an upwardly inclinedmanner and generally underlies the palm of a hand grasping the sandingmachine so that by exerting downward pressure thereon, the ball valve144 may be depressed thus admitting high pressure air into thepassageway 132 and subsequently through the passageway 128, port 126 anddown through the slot 104 in the valve member 68.

Extending rearwardly from the port 122 is a passageway 162 and extendingforwardly from the port 124 is a passageway 164. The outer end of thepassageway 162 extends downwardly as at 166 and the outer end of thepassageway 164 extends downwardly as at 168 and in each instance, thedownwardly extending passageways 166 and 168 terminate above the topedge of the longitudinal bore 22 or above the cylinders 22 and 24. Theouter limit of the passageway 166 is defined by the rear head 130 whilethe outer limit of the passageway 168 is defined by a removable fronthead 170 secured in place by fastener bolts 172 or the like.

Formed in the head 170 is a groove 174 which communicates with thepassageway 168 and also communicates with an opening 176 in a closureplug or seal 178 in the end of the cylinder 24. The head 130 is providedwith a similar passageway 180 which communicates with a similar aperture182 in an end closure plug or seal 184 in the cylinder 26. The caps orplugs 170 and 184 have their apertures adjacent the upper end thereofwhich prevents air blow-by due to the cylinder being close to the bottomof the machine. The plug 184 is retained in place by being press fittherein or retained in place by the end head.

The passageways 162 and 164 are combination exhaust and inlet ports andin one position of the valve member 68 such as is illustrated in FIGURES5 and 6, high pressure air comes in through the passageway 128, downthrough the slot or groove 104, through the port 86, through the port122 subsequently throughthe passage 122, passage 166, passage 180 andaperture 182 into the cylinder 26 for forcing the piston to the right asillustrated in FIGURE 6. The passageway 164 is then acting as an exhaustwith the exhaust products passing through the aperture 176, passageway-174, passageway 168, passageway 164, port 124, port 88, through theslot or groove 102 and down through the tubular shaft 72 for dischargefrom the bottom of the gear 74. As the piston'is forced to the right,the valve actuator 70 and the valve member 68 will be rotated a partialrevolution until such time as the groove 104 communicates with thepassageway 164 and the groove 102 communicates with the passageway 162which then will supply air through the passageway 164 to the cylinder 24and exhaust products from the cylinder 26 through the passageway 162.

The bottom of the body 16 has a recess 186 which communicates with thebore 22 in the center thereof and this bore receives the gear 74 whichis in meshing engagement with the rack gear 56. Communicating with therecess 186 is an elongated recess or groove 188 which has an oillitestrip bearing 190 secured to the outer surface thereof for hearingengagement with a reciprocating rack gear 192 which has teeth 194thereon in meshing engagement with the teeth 76 on the gear 74. Thus, asthe rack gear 56 is moved in one direction, the gear 74 is rotated thusmoving the rack gear 192 in the opposite direction. The rack gear 192 issecured to the sanding pad by the use of rivets or other suitablefasteners 196 which extend through the supporting plate for the rackgear 192 as designated by numeral 198, spacer plates 200, a connectingplate 202 and a bottom plate 204 having a sandpaper panel 206 or thelike secured thereto. A suitable cushioning pad may be provided behindthe sandpaper anel as deemed appropriate. For guiding reciprocation ofthe sandpaper pad, there is provided a pair of elongated L-shaped guidemembers 208 that are received in recesses 210 in the body 16 and securedin place by screwthreaded fasteners 212 or the like. The lower edge ofthe guide member 208 are inturned and are received under the plates 200for sliding reciprocation in relation thereto and the plates areretained in place by their connection with the body 16. Thus, as thesandpaper pad is reciprocated, the movement thereof will be guided bythe L-shaped guide members 208 sandwiched between plates 200 and 204thus retaining the structures in assembled and aligned relationship.

A spring clamp structure 214 is provided for retaining the sandpaperpanel 206 in place with the sandpaper panel having the ends thereofwrapped around the bottom plate 204 with the spring clamps 214releasable retaining the sandpaper panel 206 associated with the plate204 for abrading a surface when engaged therewith.

A hearing plate 216 underlies the gear 74 in spaced relation thereto andenables discharge of air therefrom and this plate is connected to thereciprocating sandpaper pad for reciprocation therewith and this servesto clean the working components of the sanding machine and also cleansthe work. To further seal the structure, dust seals 218 are providedalong the bottom edges of the heads 130 and 170.

The valve body 134 also is connected with a water tube or hose 220connected to a fitting 222 that is communicated with a longitudinalpassageway 224 extending into a vertical passageway 226 which in turn iscommunicated with an inclined passageway 228 extending horizontally andcommunicating with a vertical passageway 230 which communicates with atransverse passageway 232 having a pair of nozzles 234 connected to theouter ends thereof for discharging water or other solution downwardlyonto the surface being sanded. In some instances, the water supply maybe provided or eliminated as deemed necessary. A similar valve structureto that employed in connection with the air is employed including avalve stem 236 which is engaged by the undersurface of the operatinghandle for the valve thus spraying water from the nozzle 234 when theoperating handle for the valve is depressed.

During the working strokes of the piston, the air which causes movementof the piston will also expand the piston rings by entering thepassageways 46, 42 and 44 and discharging behind the rings which willexpand the rings and also serve to retain the rings in a cleancondition. The rings are retained in expanded position in both theexhaust and power stroke. The valve assembly is quite efiicient with theports in the valve member being directly across from one another so thatat the same instant that air begins to enter one cylinder, it is let outof the other cylinder. The slight slack or lag at the point ofconnection between the actuator 70 and the valve member 68 permits thevalve member to stay in open position for a period of time when thepiston is moving on the power stroke before beginning to close the inletport and in this manner, the valve assembly keeps the exhaust open onthe other side for better venting of the other cylinder.

The construction of the valve assembly including the actuator and thepiston is such that the piston is close to the center of the machinebody thus eliminating side wiggle of the machine and providesfatigueless operation. The manner of attaching the rack gear to thepiston and the construction of the rack gear itself permits the pistonto be placed very close to the bottom of the machine thus overcoming theup and down motion of the machine body.

It is pointed out that the piston travels in the opposite direction ofthe sanding shoe and by so doing, when air is driving the piston, thereis equal force of air against the cylinder head which is fastened to themachine body thus forcing the whole machine toward the direction thesanding shoe is moving. By this method, the harder you press on themachine, the more the air driving the machine will help balance themachine. In this invention, full travel on the sanding shoe is providedsince it will travel the same length as the piston does however themachine body stands still without any lost motion.

The relationship of the lobes 80 to the lobes 98 is significant inasmuchas the clearance between the lobes will determine the length of strokeof the piston and, of course, the sanding shoe. If a longer stroke isdesired, more clearance should be provided between the actuator lobes 80and the valve lobes 98 thus letting the piston travel a longer strokebefore the valve returns for the exhaust position. If the actuator andvalve lobes Were tight, the stroke would be short but much faster. Theadvantage of this type of valve is that the operator can have variousstroke lengths out of the same machine by changing the valves. This canbe done very easily by removing the valve cover cap 106, turning themachine upside down so that the valve will drop out and placing anothervalve 68 with desired lobe clearance in place. The valve 68 will fit inonly one place thus eliminating any necessity of timing.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly all suitable modifications and equivalentsmay be resorted to, falling within the scope of the invention asclaimed.

What is claimed as new is as follows:

1. An air operated sanding machine comprising a body having alongitudinal bore therein, a piston reciprocally mounted in said bore,means forming a closure for each end of the bore thus combining witheach end of the piston to form two working chambers, a sanding padunderlying the body, means reciprocally guiding the sanding pad inrelation to said body, means interconnecting the sanding pad and thepiston for reciprocating the sanding pad in opposite relation to thepiston, rotatable valve means on said body operatively connected to saidpiston for selectively admitting and exhausting air from the workingchambers along smooth curved surfaces through said valve means, saidpiston including at least one seal ring on each end thereof, and passagemeans in 8 each end portion of said piston to communicate the adjacentworking chamber with the inner surface of the seal ring for expandingthe seal ring into contacting relation with the bore thus maintaining aseal therebetween during reciprocation of the piston.

2. The structure as defined in claim 1 wherein said sanding pad includesa rack gear projecting upwardly therefrom, said piston including a rackgear attached longitudinally in the central portion thereof, said meansinterconnecting the piston and sanding pad including a rotatable gearmeshing with each of said rack gears with the rack gears being disposedon the opposite sides thereof.

3. The structure as defined in claim 2 wherein said valve means includesan actuator connected to the rotary gear, a valve member joined with thevalve actuator, interfitting joints between the valve actuator and valvemember with a variable lag space therebetween to enable variation in thecharacteristics of the stroke of the piston.

4. An air operated sanding machine comprising a body having alongitudinal bore therein, a piston reciprocally mounted in said bore,means forming a closure for each end of the bore thus combining witheach end of the piston to form two working chambers, a sanding padunderlying the body, means reciprocally guiding the sanding paid inrelation to said body, means interconnecting the sanding pad and thepiston for reciprocating the sanding paid in opposite relation to thepiston, valve means on said body operatively connected to said pistonfor selectively admitting and exhausting air from the working chambers,said piston including at least one seal ring on each end thereof, andpassage means in each end portion of said piston to communicate theadjacent working chamber with the inner surface of the seal ring forexpanding the seal ring into contacting relation with the bore thusmaintaining a seal therebetween during reiprocating of the piston, saidsanding pad including a rack gear projecting upwardly therefrom, saidpiston including a rack gear attached longitudinally in the centralportion thereof, said means interconnecting the piston and sanding padincluding a rotatable gear meshing with each of said rack gears with therack gears being disposed on the opposite sides thereof, said valvemeans including an actuator connected to the rotary gear, a valve memberjoined with the valve actuator, interfitting joints between the valveactuator and valve member with a variable lag space therebetween toenable variation in the characteristics of the stroke of the piston,said valve member including a generally cylindrical body having anarcuate slot communicating with the bottom thereof and one side wall, asecond arcuate slot communicating with the top and the side wall thereofopposite to the bottom slot, air inlet means communicated continuouslywith the top slot, and oppositely disposed passageways in said bodycommunicating with the working chambers and selectively communicatedwith the top slot and the lower slot for admitting and exhausting airfrom the working chambers.

5. The structure as defined in claim 4 wherein each end of the bore isprovided with a closure cap, said cap including an air inlet opening atthe upper end thereof communicated with the respective air passageway toprevent blow-by of the air at the bottom of the bore.

6. The structure as defined in claim 5 wherein said valve member isconnected with the actuator by generally semicircular axial extension onthe end of the valve member and the end of the actuator with theprojections being in overlapping engagement thus defining engaginglobes, said body including a retaining plug for retaining the valvemember in place thus enabling valve members having different lobecharacteristics to be inserted for varying the lag between the actuatorand the valve member for enabling inlet of air in working chamber beforethe exhaust in the other chamber is actuated to enable more effectiveventing of the other working chamber.

7. The structure as defined in claim 6 together with a manually operatedvalve in the inlet passageway, said valve including a stern projectingabove the body, and operating handle having one end connected to thebody and the other end extending in overlying spaced relation to thecentral portion of the body for engagment by the hand of a persongripping the body to enable operation of the air valve.

8. The structure as defined in claim 7 wherein said body includes a pairof water discharge nozzle means at opposite sides thereof, a watersupply passage in said body and communicated with a supply line forwater, and a manually operated valve for said water supply with themanually operated valve including a stem engaged by the operating handlefor the air thereby enabling simultaneous operation of the sandingmachine and discharge of water from said nozzle means.

9. In a pneumatic motor of the type having a reciprocating piston, avalve assembly including an actuator operatively connected to thereciprocating piston for oscil lation in response to reciprocation ofthe piston, a valve member connected with the actuator, said actuatorand valve member having overlapping and engaging axial extensions ofgenerally semi-circular configuration and including confronting lobes,at least one of said lobes being spaced from an adjacent lobe a distanceto provide a leg between the valve member and valve actuator, said valveactuator being hollow and said valve member including passagewaysdefining an exhaust passage communicating with the hollow actuator forexhaust of air therethrough before cleaning portions of a tool driven bythe motor.

References Cited UNITED STATES PATENTS 987,940 3/1911 Anderson 511701,590,353 6/1926 Ekstrom 51179 X 2,194,102 3/1940 Taylor 92182 2,635,3964/1953 Johnson 51-170 2,914,368 11/ 1959 Farmer 92184 JAMES L. JONES,1a., Primary Examiner.

